1. Field of Invention
The present invention relates to a method for manufacturing an interconnect. More particularly, the present invention relates to a method for manufacturing a diffusion barrier layer to block copper atoms diffusing from the copper wires.
2. Description of Related Art
In the procedure for manufacturing an ultra large scale integration circuit, more than one hundred thousand transistors are disposed on a silicon surface with an area of only about 1 to 2 square centimeters. Additionally, in order to increase the integration of the integrated circuit, the density of the conductive wire used to electrically connect the transistors and the devices with each other are also increased. Therefore, in accord with the increased interconnects manufacturing requirements of miniaturized transistors, it is increasingly necessary for IC manufacturing to adopt a design with more than two metal layers. In particular, a number of multi-function products, such as microprocessors, even require 4 or 5 metal layers to complete the internal connections thereof.
With the decreasing size of the device, the distance between the adjacent conductive wires is decreased. In the extremely narrow space, unexpected capacitive and inductive coupling occurs between the parallel conductive wires and the capacitive and inductive coupling leads to interference between the conductive wires. Due to the interference between the conductive wires, the resistance-capacitance time delay (RC time delay) between the conductive wires is increased. The data transmission rate is especially repressed by the capacitive and inductive coupling when the data are transmitted through the parallel conductive wires at a relatively high transmission rate. Hence, the energy waste is greatly increased and the efficiency of the device is limited.
Copper is currently the substitute of choice for aluminum interconnect material, because its high anti-electromigration and low resistance permit a decreased time delay of signal transmission Therefore, the resistance of the conductive wire can be decreased.
However, the use of copper as an interconnection material presents several problems. For example, copper oxidizes easily at low temperatures and copper diffuses easily into silicon dioxide and other dielectric materials used in micro-circuitry. Therefore, in order to overcome the disadvantages of using copper wires, it is necessary to passify surfaces of copper wires and provide diffusion barrier layers between copper and adjacent layers.